Implement rust_eh_personality in Rust, remove rust_eh_personality_catch.
Well, not quite: ARM EHABI platforms still use the old scheme -- for now.
r? @alexcrichton
Long ago we discovered that threads which outlive main and then exit while the
rest of the program is exiting causes Windows to hang (#20704). That's what was
happening in this test so let's just not run this test any more.
Use the same procedure as Python to determine whether a character is
printable, described in [PEP 3138]. In particular, this means that the
following character classes are escaped:
- Cc (Other, Control)
- Cf (Other, Format)
- Cs (Other, Surrogate), even though they can't appear in Rust strings
- Co (Other, Private Use)
- Cn (Other, Not Assigned)
- Zl (Separator, Line)
- Zp (Separator, Paragraph)
- Zs (Separator, Space), except for the ASCII space `' '` (`0x20`)
This allows for user-friendly inspection of strings that are not
English (e.g. compare `"\u{e9}\u{e8}\u{ea}"` to `"éèê"`).
Fixes#34318.
[PEP 3138]: https://www.python.org/dev/peps/pep-3138/
Added empty CloseDelim to tokens for future use.
Description says it all. I added a new DelimToken type, Empty, to indicate a Delimited tokenstream with no actual delimiters (which are variously useful for constructing macro output).
r? @nrc
The type equation in projection takes place under a binder and a snapshot, which
we can't easily take types out of. Instead, when encountering a projection error,
try to re-do the projection and find the type error then.
This fails to produce a sane type error when the failure was a "leak_check" failure.
I can't think of a sane way to show *these*, so I just left them use the old crappy
representation, and added a test to make sure we don't break them.
Refactor constant evaluation to use a single error reporting function
that reports a type-error-like message.
Also, unify all error codes with the "constant evaluation error" message
to just E0080, and similarly for a few other duplicate codes. The old
situation was a total mess, and now that we have *something* we can
further iterate on the UX.
Unfortunately, projection errors do not come with a nice set of
mismatched types. This is because the type equality check occurs
within a higher-ranked context. Therefore, only the type error
is reported. This is ugly but was always the situation.
I will introduce better errors for the lower-ranked case in
another commit.
Fixes the last known occurence of #31173
Add a method to the mpsc::Receiver for producing a non-blocking iterator
Currently, the `mpsc::Receiver` offers methods for receiving values in both blocking (`recv`) and non-blocking (`try_recv`) flavours. However only blocking iteration over values is supported. This PR adds a non-blocking iterator to complement the `try_recv` method, just as the blocking iterator complements the `recv` method.
Use-case
-------------
I predominantly use rust in my work on real-time systems and in particular real-time audio generation/processing. I use `mpsc::channel`s to communicate between threads in a purely non-blocking manner. I.e. I might send messages from the GUI thread to the audio thread to update the state of the dsp-graph, or from the audio thread to the GUI thread to display the RMS of each node. These are just a couple examples (I'm probably using 30+ channels across my various projects). I almost exclusively use the `mpsc::Receiver::try_recv` method to avoid blocking any of the real-time threads and causing unwanted glitching/stuttering. Now that I mention it, I can't think of a single time that I personally have used the `recv` method (though I can of course see why it would be useful, and perhaps the common case for many people).
As a result of this experience, I can't help but feel there is a large hole in the `Receiver` API.
| blocking | non-blocking |
|------------|--------------------|
| `recv` | `try_recv` |
| `iter` | 🙀 |
For the most part, I've been working around this using `while let Ok(v) = r.try_recv() { ... }`, however as nice as this is, it is clearly no match for the Iterator API.
As an example, in the majority of my channel use cases I only want to check for *n* number of messages before breaking from the loop so that I don't miss the audio IO callback or hog the GUI thread for too long when an unexpectedly large number of messages are sent. Currently, I have to write something like this:
```rust
let mut take = 100;
while let Ok(msg) = rx.try_recv() {
// Do stuff with msg
if take == 0 {
break;
}
take -= 1;
}
```
or wrap the `try_recv` call in a `Range<usize>`/`FilterMap` iterator combo.
On the other hand, this PR would allow for the following:
```rust
for msg in rx.try_iter().take(100) {
// Do stuff with msg
}
```
I imagine this might also be useful to game devs, embedded or anyone doing message passing across real-time threads.
Add MIR Optimization Tests
I've starting working on the infrastructure for testing MIR optimizations.
The plan now is to have a set of test cases (written in Rust), compile them with -Z dump-mir, and check the MIR before and after each pass.
feat: reinterpret `precision` field for strings
This commit changes the behavior of formatting string arguments with both width and precision fields set.
Documentation says that the `width` field is the "minimum width" that the format should take up. If the value's string does not fill up this many characters, then the padding specified by fill/alignment will be used to take up the required space.
This is true for all formatted types except string, which is truncated down to `precision` number of chars and then all of `fill`, `align` and `width` fields are completely ignored.
For example: `format!("{:/^10.8}", "1234567890);` emits "12345678". In the contrast Python version works as the expected:
```python
>>> '{:/^10.8}'.format('1234567890')
'/12345678/'
```
This commit gives back the `Python` behavior by changing the `precision` field meaning to the truncation and nothing more. The result string *will* be prepended/appended up to the `width` field with the proper `fill` char.
__However, this is the breaking change, I admit.__ Feel free to close it, but otherwise it should be mentioned in the `std::fmt` documentation somewhere near of `fill/align/width` fields description.
